TUN-4153: Revert best-effort HTTP2 usage when talking to origins

This commit reverts part of 1cf6ae37eb.

CHANGES.md

@@ -1,5 +1,12 @@
 **Experimental**: This is a new format for release notes. The format and availability is subject to change.
 
+## 2021.3.6
+
+### Bug Fixes
+
+- Reverted 2021.3.5 improvement to use HTTP/2 in a best-effort manner between cloudflared and origin services because
+  it was found to break in some cases.
+
 ## 2021.3.5
 
 ### Improvements

ingress/origin_service.go

@@ -15,8 +15,6 @@ import (
 	"github.com/pkg/errors"
 	"github.com/rs/zerolog"
 
-	"golang.org/x/net/http2"
-
 	"github.com/cloudflare/cloudflared/hello"
 	"github.com/cloudflare/cloudflared/ipaccess"
 	"github.com/cloudflare/cloudflared/socks"
@@ -289,7 +287,6 @@ func newHTTPTransport(service originService, cfg OriginRequestConfig, log *zerol
 		httpTransport.DialContext = dialContext
 	}
 
-	http2.ConfigureTransport(&httpTransport)
 	return &httpTransport, nil
 }